| Biomass,as the only renewable energy category with diversified utilization,has the advantages of abundant reserves,wide distribution,and environmentally friendly,and it has been praised as the world’s fourth largest energy after fossil fuels(natural gas,oil,and coal).Also,biomass is the most promising zero-carbon resource.Its large-scale utilization can effectively reduce the dependence of the energy industry on fossil resources,significantly reduce CO2 emissions,and assist in economic circulation development.Thus,it has become an important direction of energy industry development.Promoting the utilization of biomass is an effective technological way to achieve carbon peaking and carbon neutrality goals and is also an important task for energy saving,emissions reduction.and environmental protection in China.It is of great significance for the achievement of China’s goals of carbon emission peak and carbon neutrality.Pyrolysis is a highly promising technology for the thermochemical conversion of biomass.Through disposal of biomass under anaerobic or microaerobic conditions,the efficient separation of volatile fraction and pyrolysis carbon can be achieved,and through further rapid condensation of pyrolysis volatiles,biomass can be rapidly transformed into a variety of resource-based products such as bio-oil,bio-gas,and bio-char,which is an important way to realize the diversified utilization of biomass.As reported,over 400 substances are contained in biooil,including high-quality chemicals,and their selective preparation can effectively relieve the dependence on fossil fuels.However,the composition and structure of biomass are extremely complex,and there are thousands of reaction pathways during the pyrolysis process,so if not selectively controlled,it is hardly to obtain target products.Therefore,it is urgent to develop selective catalytic pyrolysis technology based on the compositions and structural characteristics of different biomass,to selectively regulate the pyrolysis process and achieve the selective preparation of specific target products.Thus,this paper conducted related research on selective pyrolysis technology for biomass rich in cellulose,lignin,and ferulic acid,and several feasible technologies were formed for the preparation of typical anhydrosugars and phenols,as follows.Firstly,the technology on selective preparation of 1-hydroxy-3.6dioxabicyclo[3.2.1]octan-2-one(LAC)based on cellulose was developed.Under the catalysis of metal-loaded nitride HZSM-5(Mg/N-HZSM-5),LAC can be selectively prepared via the catalytic pyrolysis of cellulose.The effect of the species and loading of modified metal,pyrolysis temperature,and catalyst-to-cellulose ratio on the yield and selectivity of LAC were investigated via pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS).The results indicated that the LAC yield based on cellulose was up to 7.48 wt%,accompanied with a selectivity of 30.33%based on bio-oil.After that,a lab-scaled setup was used to further evaluate the feasibility of the LAC preparation technology.The maximal yield of LAC based on cellulose was 6.69 wt%,accompanied by a selectivity of 26.18%.It needs to be noted that the yield and selectivity of LAC were slightly lower than that obtained from Py-GC/MS,which is mainly caused by the poor mixing between catalyst and cellulose.Secondly,the technology on selective preparation of levoglucosenone(LGO)and furfural(FF)based on typical cellulosic biomass was developed.Under the catalysis of ammonium dihydrogen phosphate(NH4H2PO4),LGO and FF can be selectively prepared via the catalytic pyrolysis of rice husk.The effect of the loading of NH4H2PO4 and pyrolysis temperature on the yield and selectivity of LAC was investigated via Py-GC/MS.The enrichment of some specific products such as hydrocarbons,anhydrosugars,furans,and phenolics obtained from the two-stage pyrolysis process was analyzed.The result indicated that the bio-oil obtained from first-stage pyrolysis of rice hush was rich in LGO and FF.The selectivity of LGO and FF was up to 34.65%and 20.98%,which can be obtained from the pyrolysis of rice husk pretreated with the NH4H2PO4 loading of 8.63 wt%at 390℃.While the bio-oil obtained from second-stage pyrolysis can be used for fuel application.Thirdly,the technology on selective preparation of phenol based on typical lignocellulosic biomass was developed.Under the catalysis of magnetic solid base(K3PO4/Fe3O4),phenol can be selectively prepared via the catalytic pyrolysis of poplar.The effect of pyrolysis atmosphere(N2,H2,and simulated gas),pyrolysis temperature(400-700℃),catalyst-to-biomass ratio(0,0.1,0.5,1,1.5,and 2),and biomass materials on the yield and selectivity of phenol were investigated via lab-scaled setup.The maximal phenol yield based on poplar was up to 4.3 wt%,accompanied with the phenol selectivity of 17.6%based on bio-oil.Notably,the magnetic solid base can be easily recovered due to the usage of magnetic Fe3O4,which afford a convenient way to achieve the recycling of the catalyst after the catalytic pyrolysis process.Finally,the technology on selective preparation of 4-vinyl phenol(4-VP)based on typical biomass rich in p-coumaric acid(p-CA)was developed.p-CA is a phenolic precursor that mainly exists in herbaceous biomass such as bagasse.It is commonly connected to other components by an unstable ester bond or ether bond.Based on this,bagasse was pretreated with different alkaline substances to break down its cell wall structure,and thus,more p-CA can be released to enable the high-selective preparation of 4-VP at lower temperatures.The effect of alkali type(NaOH.Ca(OH)2.NaiCOs),alkali content(0-10 wt%),pyrolysis temperature(220-370℃),and pretreatment time(1-60 min)on 4-VP formation was investigated.During the pyrolysis of bagasse,pretreated 10 min by 1 wt%Ca(OH)2,the maximal yield of 4-VP obtained from Py-GC/MS and lab-scaled setup was 6.37 wt%and 6.57 wt%,respectively,which was significantly higher than that obtained from non-catalytic pyrolysis of pure bagasse. |
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